There are claims the Syrian Government has attacked its own people with chemical weapons.As many as 13-hundred people are said to have been killed, according to opposition groups. The Syrian Government says it's not to blame but the United Nations is demanding an investigation.

Transcript

TONY JONES, PRESENTER: Britain and France have called for the international community to consider reacting with force if yesterday's claims of a chemical weapons attack by the Assad regime in Syria are proven.

More than 35 countries have called for UN inspectors in Syria to be given immediate access to the site of the incident in Damascus.

Syria's rebels say more than 1,300 people have been killed, many of them women and children, although there's been no independent verification of the death toll.

The Syrian Government has strongly denied it was to blame.

Shaun Hassett reports, and a warning: this story does contain disturbing images.

SHAUN HASSETT, REPORTER: While the world focuses on the possible use of chemical weapons in Damascus, the Syrian capital is still dealing with the daily struggles of conventional warfare.

Rebel activists say yesterday's alleged chemical attack was followed up by an aerial bombardment.

The Assad regime has confirmed it's carrying out an offensive in Damascus, but it's strongly denied that chemical weapons are part of it.

OMRAN ZOABI, SYRIAN INFORMATION MINISTER (voiceover translation): Everything that has been said is absurd, primitive, illogical and fabricated. What we say is what we mean. There is no use of chemical weapons at all, at least not by the Syrian Army or the Syrian state and it's easy to prove. The military operation taking place on the ground is successful. The allegation has been fabricated in advance by the opposition as they knew that this is the first day of the inspectors' mission.

SHAUN HASSETT: Even so, it is clear something horrible has happened in Damascus. These are just some of the images that have been posted to social media. They purportedly show the aftermath of a chemical attack that has left hundreds of civilians dead.

TAMARA ALFRIFAI, HUMAN RIGHTS WATCH: It is extremely alarming. It just adds another dimension to the ongoing conflict in Syria. If the reports are true, if the attacks are verified, it really adds another layer of complexity to the series of abuses that we've been documenting in that country. This is not the first time we witness a serious violation of international law and of human recognise law, but this is really a major one. The pictures are shocking. The images leave us voiceless.

SHAUN HASSETT: Forensic experts say faking an incident on this scale isn't possible, although some have expressed guarded scepticism.

STEPHEN JOHNSON, CRANFIELD UNI. FORENSICS INSTITUTE: There are, within some of the videos, examples which seem a little hyper-real and almost as if they've been set up, which is not to say that they are fake, but it does cause some concern. Of course there are lot of dead bodies, so it may be that we're just looking at the video too late on into the incident.

SHAUN HASSETT: But Stephen Johnson does say many of the victims appear to show symptoms consistent with an attack of sarin nerve gas.

STEPHEN JOHNSON: Looking at the videos, my first impressions are that there's a large number of people demonstrating the shaking of limbs, dilation of pupils in some cases, which would be consistent with some kind of trauma to the nervous system. These symptoms aren't consistent amongst everyone, but they're certainly present and they're similar to lot of videos we've seen over the last year.

SHAUN HASSETT: The international community is keen to get to the bottom of it. More than 35 countries have called for UN inspectors in Syria to be given access to the site immediately and France says there must be consequences if the rebel's claims are proven.

LAURENT FABIUS, FRENCH FOREIGN MINISTER (voiceover translation): If it's confirmed, France's position is that there must be a reaction. What does that mean? Not sending troops on the ground, but a reaction, not only of international condemnation, but a reaction that could take the shape of the use of force.

SHAUN HASSETT: The UN Security Council has called for a thorough, impartial and prompt investigation, although Russia and China have blocked any formal declaration.